Products for Disease Protection for Hawthorn Trees

Depending on the species, Hawthorn trees (Crataegus spp.) grow throughout U.S. Department of Agriculture plant hardiness zones 4 through 9. These medium- to large-sized trees are susceptible to various diseases, including powdery mildew, fire blight, rust, scab and leaf spot. Several products are readily available to protect this stunning tree from attacks from these diseases.

Dormant Oil

Dormant oils were once applied only during the tree’s dormant period because they consisted of heavy oil, which would damage leaves and buds. Newer dormant oils, however, use lighter oils that don’t harm the tree and are safe for use anytime during the season. Nowadays, "dormant oil" generally refers to the application time of the spray. When applied in the winter, dormant oils control overwintering insects and prevent powdery mildew infections.

Fungicides

Fixed copper, copper soap and Bordeaux mixture are versatile fungicides used to control and prevent various fungal and bacterial diseases affecting hawthorn trees. Copper fungicides control Entomosporium leaf spot, rust, scab and fire blight, and can be used as a protective spray applied during the dormant season to keep diseases from attacking the tree. Containing inorganic sulfur and lime, lime sulfur fungicide is used during the tree’s dormant period or throughout the growing season. It is also safe to mix with oil pesticides to help control insects, as well as fungal diseases. Apply lime sulfur fungicide only when temperatures are below 80 degrees Fahrenheit. Consider applying the treatment in the late evening or early morning hours to prevent burning the leaves.

Homemade Protectant Recipes

A few homemade protectant sprays control pests on hawthorn trees. Cornell University created a homemade dormant oil recipe that consists of inexpensive ingredients that gardeners can purchase at department stores or garden centers. This formula prevents various foliar diseases -- such as leaf spots -- and overwintering insects, and contains 1 tablespoon of baking soda, 2 tablespoons of fine canola oil and 1 gallon of cool water. Another homemade recipe for dormant protectant spray contains 5 tablespoons of hydrogen peroxide, 2 tablespoons of baking soda, 2 tablespoons of castile soap and 1 gallon of lukewarm water.

Chlorothalonil

A protectant fungicide spray, chlorothalonil is applied to the foliage of the hawthorn tree before the disease infects the plant and can be used to prevent Entomosporium leaf spot in trees that have been previously infected with the fungal disease. This broad-spectrum fungicide is a nonsystemic contact foliar spray and requires thoroughly covering the foliage with the fungicide in order to effectively prevent diseases. Chlorothalonil has a low toxicity to humans, mammals and natural enemies, and is safe to use on fruit trees, vegetables and ornamental plants.

About the Author

Amanda Flanigan began writing professionally in 2007. Flanigan has written for various publications, including WV Living and American Craft Council, and has published several eBooks on craft and garden-related subjects. Flanigan completed two writing courses at Pierpont Community and Technical College.